﻿// The MIT License(MIT)
//
// Copyright(c) 2021 Alberto Rodriguez Orozco & LiveCharts Contributors
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in all
// copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
// SOFTWARE.

using System;
using System.Threading.Tasks;

namespace LiveChartsCore.Kernel;

/// <summary>
/// An object that is able to throttle an action.
/// </summary>
public class ActionThrottler
{
    private readonly object _sync = new();
    private readonly Func<Task> _action;
    private bool _isWaiting = false;

    /// <summary>
    /// Initializes a new instance of the <see cref="ActionThrottler"/> class.
    /// </summary>
    /// <param name="targetAction">The target action to throttle.</param>
    /// <param name="time">The throttling time.</param>
    public ActionThrottler(Func<Task> targetAction, TimeSpan time)
    {
        _action = targetAction;
        ThrottlerTimeSpan = time;
    }

#if DEBUG
    /// <summary>
    /// Gets the calls.
    /// </summary>
    /// <value>
    /// The calls.
    /// </value>
    public int Calls { get; private set; } = 0;
#endif

    /// <summary>
    /// Gets or sets the throttler time span.
    /// </summary>
    /// <value>
    /// The throttler time span.
    /// </value>
    public TimeSpan ThrottlerTimeSpan { get; set; }

    /// <summary>
    /// Schedules a call to the target action.
    /// </summary>
    /// <returns></returns>
    public async void Call()
    {
        lock (_sync)
        {
#if DEBUG
            Calls++;
#endif

            if (_isWaiting) return;
            _isWaiting = true;
        }

        await Task.Delay(ThrottlerTimeSpan);

        // notice it is important that the unlock comes before invoking the Action
        // this way we can call the throttler again from the Action
        // otherwise calling the throttler from the Action will be ignored always.
        lock (_sync)
        {
            _isWaiting = false;
        }

        await _action();
    }

    /// <summary>
    /// Forces the call to the target action, this call is not throttled.
    /// </summary>
    /// <returns></returns>
    public void ForceCall()
    {
        _action().GetAwaiter().GetResult();
    }
}
